- /* Given a symbol VAR, and a stack frame id FRAME, read the value
- of the variable an return (pointer to a) struct value containing
- the value.
+ /* Given a symbol VAR, the corresponding block VAR_BLOCK (if any) and a
+ stack frame id FRAME, read the value of the variable and return (pointer
+ to a) struct value containing the value.
+
+ VAR_BLOCK is needed if there's a possibility for VAR to be outside
+ FRAME. This is what happens if FRAME correspond to a nested function
+ and VAR is defined in the outer function. If callers know that VAR is
+ located in FRAME or is global/static, NULL can be passed as VAR_BLOCK.